The present disclosure relates to railroad freight cars and in particular to cars of the type incorporating a tall center beam structure extending along the length of the car body between a pair of bulkheads located at the ends of the car body.
Center beam railroad cars, also called center partition bulkhead flat cars, have been used for more than three decades to carry materials such as lumber and sheets of building materials that can be contained in packages of uniform size and shape. Such center beam cars have repeatedly been redesigned in attempting to reduce tare weight yet provide ample strength to resist dead weight forces of lading as well as the dynamic forces produced by movement of such a car as a part of a train. Lighter weight in such cars advantageously allows carriage of additional revenue-bearing cargo while the laden car remains within limits on the maximum loading which can be imposed on the rails. Additionally, a lighter car requires less fuel when being moved unladen.
A shorter overhanging portion of a freight car, the portion longitudinally outboard of the supporting center bearing, reduces the likelihood of derailment caused by compression or tension forces between adjacent cars of a train.
Various stages of development of such center beam cars are represented in prior art patents such as Wagner U.S. Pat. No. 3,734,031, Baker U.S. Pat. No. 4,543,887, Harris et al. U.S. Pat. No. 4,681,041, Butcher et al. U.S. Pat. No. 4,802,420, Saxton U.S. Pat. No. 5,758,584, and Clark, et al. U.S. Pat. Nos. 6,470,808 and 6,550,398. The cars disclosed in these patents all include bulkheads at the opposite ends of a car body and an upright longitudinally-oriented center beam including the center sill of the car body, a top chord interconnecting the tops of the bulkheads, and a vertical structure interconnecting the center sill with the top chord along the length of the car body.
What is desired, then, is an improved center beam car of lighter weight than previously has been thought practical, yet which has ample strength to withstand the forces imposed by greater weights of lading than could be carried safely by previously-known cars. Desirably, such a car would also have a short longitudinal overhang.